One of the major tasks for the ultrasound generated by laser is the discussion of the two regimes: thermoelastic regime and ablation regime,and each of the theoretical directivity patterns are mentioned. Based on the effect of array factor,a newly method of the laser ultrasonic generated by a phased array of laser beams was proposed. This means,a method to make the ultrasound field be steered and amplified in a particular direction,can be designed and implemented to enhance the signal propagation in the region of interest. It will be more significant to apply ultrasound generated by this method in nondestructive testing of materials and products. The corresponding system has been completed in practice.